85 Johnson won't stay running unless its constantly primed.

[badford]

Hi, I just upgraded the 76 35hp Johnson on my boat to a 85 Johnson 60hp (2cyl). The motor hadn't been run in 5 years IMO. So, after looking at the spark plugs & seeing if it had compression, I hung it on the back of my boat. It is the VRO model, & didn't come with the oil tank. No mater, I'm a fan of premix. I just capped off the oil side & swapped out the old fuel lines. Before cranking it over I put a little bit of permix in the cylinders via the spark plug holes. I also replaced the plugs & checked for spark. Also, I thought it would be a good idea to see if the water pump was working, so I cranked it over without the plugs in untill water was coming out the drain hole. Then the moment of truth. Cranked over just fine. & cranked & cranked. Then I used a sirenge to add fuel into the carbs. As soon as I hit the starter, she fired up. Ok. Got 2 carb kits & rebuilt them like I should have done in the first place. Still wouldn't run. Using the bulb in the fuel line to make sure there was presure, I noticed fuel oozing out from the oil/fuel pump. Replaced it with a fuel only pump & plugged the vacuum line at the block (the fuel pump attaches directly to the block & has a vacuum hole there). Now, if I use the primer, it starts. It doesn't stay running unless I keep hitting the primer though. I took the carbs back off & checked with the old gaskets to make sure I wasn't blocking any passages & to see if I made some other foolish mistake. They both had fuel in the bowels. I went & blew carb cleaner through all the passage ways, again, & even squirted alcohol in them, followed by compressed air.Didn't find any clogs or other problems. I've seen more pieces on lawn mower carbs. There's not much you could do wrong with them. They have low & high speed jets, both are fixed. The only adjustments you can make are to the float. It seems as if it just won't siphon any gas into the thoats of the carbs. I thought maybe the air box "has" to be on to cause some air restriction thus creating more vacuum to pull gas into the motor. But no. & that's where I'm at now. A complete loss. Anyone have some recomandations? I have no idea what else to try.

 

[RPJS]

Re: 85 Johnson won't stay running unless its constantly primed.

When you crank the motor have you noticed any blow back out of the carbs, I'm thinking maybe the reed valves aren't shutting correctly.

 

[Silvertip]

Re: 85 Johnson won't stay running unless its constantly primed.

Disconnect the outlet side of the fuel pump and crank the engine. If there is no fuel flow, either the pump is bad or a vacuum signal is not getting to the pump for operation. There must be a gasket between the pump and engine block to seal that vacuum port.

 

[Silvertip]

Re: 85 Johnson won't stay running unless its constantly primed.

One more thing. Make sure that vaccum port on the block is actually drilled out. If it had a screw in it you can assume it is open.

 

[badford]

Re: 85 Johnson won't stay running unless its constantly primed.

When you crank the motor have you noticed any blow back out of the carbs, I'm thinking maybe the reed valves aren't shutting correctly.

It doesn't look like any blow back. I looked at the reeds when I had the carbs off & they looked to be in good condition. By that I mean they were all closed & no visable cracks.

 

[badford]

Re: 85 Johnson won't stay running unless its constantly primed.

Disconnect the outlet side of the fuel pump and crank the engine. If there is no fuel flow, either the pump is bad or a vacuum signal is not getting to the pump for operation. There must be a gasket between the pump and engine block to seal that vacuum port.

The vacuum port had a screw in it. I made a gasket & I also used clear gas line so I could see when gas gets to the pump, manifold & then the carbs. Once I've squeezed the inline bulb, the pump has no problem keeping preasure to the carbs. Fuel is getting as far as the carb bowls.

 

[84CJ7]

Re: 85 Johnson won't stay running unless its constantly primed.

If those are the carbs I think they are then its the tiny brass straws that go from the bottom of the bowls all the way up through the carbs, they are small enough where it takes a single bristle from a wire brush or something to clean them, and you usually have to alternate between soaking them in carb cleaner and blowing high pressure compressed air through them. They are also narrowest at the bottom opening so if u can poke that clear usually you can dissolve and blow out the rest. If thats the carbs I think then it'll also have rubber gaskets and a rubber tip on the float needle that go to **** in a hurry with regular carb cleaner on them so be careful.
When they are clear you will be able to blow through the top jet on the front and feel air from the brass needle on the bottom, but that doesnt mean they are totally clear yet.

 

[badford]

Re: 85 Johnson won't stay running unless its constantly primed.

If those are the carbs I think they are then its the tiny brass straws that go from the bottom of the bowls all the way up through the carbs, they are small enough where it takes a single bristle from a wire brush or something to clean them, and you usually have to alternate between soaking them in carb cleaner and blowing high pressure compressed air through them. They are also narrowest at the bottom opening so if u can poke that clear usually you can dissolve and blow out the rest. If thats the carbs I think then it'll also have rubber gaskets and a rubber tip on the float needle that go to **** in a hurry with regular carb cleaner on them so be careful.
When they are clear you will be able to blow through the top jet on the front and feel air from the brass needle on the bottom, but that doesnt mean they are totally clear yet.

Sounds like the same carbs. You're talking about the 3/32" tube inside the larger 1/4" or so tube? I felt air coming out when blown through the top jet & plugging the 2 holes in the top of the throat. I also ran alcohol through them. But at this point, I'll take them off...again. You may be right, the old gaskets were desentigrading & pieces could have gotten lodged in there.

Thanks to you & the others for the ideas. I'll let you know one way ot the other.

 

[ob]

Re: 85 Johnson won't stay running unless its constantly primed.

I agree on the carb bowl pickup tubes.You can also use a set of indexed torch tip cleaners to insure they are unrestricted.Just select the one that fits the hole best.
Welcome to iboats goodchevy....I mean badford.

 

[badford]

Re: 85 Johnson won't stay running unless its constantly primed.

I agree on the carb bowl pickup tubes.You can also use a set of indexed torch tip cleaners to insure they are unrestricted.Just select the one that fits the hole best.
Welcome to iboats goodchevy....I mean badford.

Well I gotta say there are some pretty sharp people here. 84cj7 hit it right on. Thank you very much. She fired right up. Runs a bit rough & spits a little gas back out the idle jets. Maybe the reeds like RPJS mentioned? Thank you OB for welcoming me & for the excellent idea for a cleaning apparatus. Of course you know, repair manuals strictly forbid such manuvers. Who goes by the books anyway. & OB, lets not bring automobile flavors into this huh, least I have to tell you about my 58 chevy with a 9in & soon home of a efi BBF.
Thanks again